Well re-entry tool with bumperhead

ABSTRACT

To prevent damage to an orienting device used for re-entry into wells located on the floor of a body of water on which a guide cone is mounted a bumperhead is mounted on the lower end of the tubing string carrying the orienting device.

United States Patent [191 Shatto, Jr. et al.

[ Jan. 29, 1974 WELL RE-ENTRY TOOL WITH BUMPERHEAD [75] Inventors:Howard L. Shatto, Jr.; Johannes A.

W. J. Van Dommelen, both of The Hague, Netherlands [73] Assignee: ShellOil Company, New York, NY.

[22] Filed: Dec. 2, 1971 [21] Appl. No.: 204,046

[30] Foreign Application Priority Data Mar. 10, I971 Great Britain6,446/71 [52] U.S. Cl. 166/.5, 175/5 [51] Int. Cl .1 E21b 7/12, E21b33/035 [58] Field of Search 166/5, .6; 175/5, 7; 340/3, 340/6, 8 FT [56]References Cited UNITED STATES PATENTS 3,199,613 8/1965 Malott et al.175/5 3,458,853 7/ 1969 Daniels et al. 3,516,492 6/1970 Petersen3,547,189 12/1970 Bielstein et a1. 3,222,634 12/1965 Foster 3,491,842l/l970 Delacour et al. 175/7 X Primary ExaminerMarvin A. ChampionAssistant Examiner-Lawrence J. Staab [5 7] ABSTRACT To prevent damage toan orienting device used for reentry into wells located on the floor ofa body of water on which a guide cone is mounted a bumperhead is mountedon the lower end of the tubing string carrying the orienting device.

9 Claims, 6 Drawing Figures PATENTEDmz 1914 SHEEI 3 0F 3 FIGS WELLRE-ENTRY TOOL WITH BUMPERHEAD BACKGROUND OF THE INVENTION The presentinvention relates to a well re-entry tool used for re-entering a welllocated below the water level and for making a tubular connection withsaid well from a vessel or platform structure floating on the surface ofthe water.

It has long been known to drill wells into underground formations lyingbelow the sea bottom. The entrances to these wells are often locatedabove the water level, in which case fixed structures mounted on the seabottom are used to support the riser pipe of the well and the wellheadmounted thereon. After completion, re-entry of the well for work-overoperations is relatively easy since these operations can be carried outfrom a platform mounted on the structure above the water level.

However, not all wells have a wellhead installed above water level.Completing wells below sea level is often attractive when the wells arelocated in areas with dense shipping traffic, or in areas that arenotorious for bad weather. Re-entry of such wells may then take place bymeans of guide lines, each having one end attached to the wellhead, andthe other end attached to a buoy. The guide lines are picked up from awork-over vessel by retrieving the buoys, whereupon equipment forre-entering the well is guided along the lines onto the submergedwellhead. To guide the equipment into the well entrance, this entrancemay be provided with a guide means consisting of a conical funnelmounted with the small diameter part thereof on the well entrance.

When no guide lines are used, communication with a submerged well can beestablished by lowering a tube to the location where the well isexpected to be, with an orienting device such as a television camera orequipment known by the trade name Sonar on the lower end of the tube.Propulsion means are arranged on the tube, which can displace the tubeduring lowering thereof, so that it will land in the center of thewellhead. The position of the tube with respect to the wellhead iscontinuously watched by the operator on the monitor of the orientingdevice, and any deviation from the required position, i.e., anydeviation from a line extending vertically through the axis of the wellentrance, is compensated by the action of the propulsion means which arecontrolled by the operator (or automatically) by varying the directionand magnitude of thrust exerted by the propulsion means.

A suitable propulsion means for controlling the position of a tubingstring which is applied for re-entering a submerged well, is a jetnozzle which is formed by an opening in the wall of the tubing string.By supplying pressurized water to the string, the water flow issuingfrom this opening will laterally displace the pipe in a directionopposite to the direction of the water flow. Displacement of the pipe ina rotational sense will enable the operator to displace the lower end ofthe pipe in any desired direction. By varying the pressure of the waterjet, the distance over which the lower end of the pipe is displaced canbe controlled. Suitable valve sleeve means may be provided to open orclose the entrance to the jet opening at will.

The entrance to the well is preferably provided with a guide meanscomprising a conical funnel mounted Lli with the small diameter partthereof on the entrance of the well and having a number of reflectorsmounted around the large diameter part thereof, said reflectors beingsuitable for reflecting the signals of the orienting device so that aclear indication of these reflectors will be visible on the monitor ofthe orienting device.

An unobstructed view of the wellhead entrance, which by means of theguide funnel and the reflectors connected thereto is distinguishablefrom any other objects lying on the sea bottom, can be obtained if theorienting device is mounted below the lower end of the tube which is tobe let down on the wellhead entrance. Moreover, the orienting deviceshould preferably be in the center of the tube to increase the accuracyof operation.

In known equipment, the orienting device is mounted in the lower exit ofthe tube and extends partly therefrom. The device is suspended from acable, by which it can be lowered into its operative position in thelower part of the tube. The tube is lowered towards the sea bottom andat the same time maneuvered by the propulsion means to a location inwhich the lower end of the tube is above the center of the guidecone.The orienting device is then retracted by the cable into the tube beforethe latter is lowered to enter the guide cone. This retraction of theorienting device is necessary to prevent damage thereof by the innerwall of the guide cone.

SUMMARY OF THE INVENTION A drawback of this known system is that duringthe descent of the tube the last few feet of this descent has to becovered blind, as the orienting device is retracted within theprotective shroud formed by the lower end of the wall of the tube.

An object of the present invention is to provide a well re-entry toolfor use in combination with a conical guide funnel, the position ofwhich tool can be controlled over the lower part of the descent of thetool by means of an orienting device and a propulsion means.

Another object of the present invention is to provide a well re-entrytool which can be lowered from a vessel or floating structure onto awellhead entrance without damaging the orienting device used forindicating the position of the tool relative to the well entrance.

Still another object of the invention is to provide a well re-entry toolwhich can be lowered into a submerged wellhead within a relatively shorttime and with only a minimum chance of failure.

A further object of the invention is to provide a well re-entry toolwhich can be automatically connected to and controllably released fromthe wellhead.

According to the invention, a well re-entry tool for use in combinationwith a guide funnel comprises a tube provided with connecting means atits upper end suitable for connection to another tube, and with aninternal seat at its lower end suitable for supporting an orientingdevice, which orienting device when supported by the internal seat ispartly within the tube and partly extends beyond the lower end of thetube, and a bumper head on the lower end of the tube, the lateraldimensions of the bumper head being sufficient to prevent the orientingdevice from contacting the inner wall of the guide funnel when thebumper head touches this inner wall in a position in which thelongitudinal axes of the tube and the funnel are substantially parallel.

BRIEF DESCRIPTION OF THE DRAWING The invention will now be describedwith reference to the drawing, in which some embodiments of theinvention are shown by way of example in which:

FIG. 1 represents a vertical section over a submerged well entrance, onwhich a well re-entry tool is being lowered.

FIG. 2 shows a vertical section of a submerged well entrance, on which awell re-entry tool of an alternate construction from the tool shown inFIG. 1 and over which re-entry tool a marine riser has been guided intothe wellhead for coupling the lower end of the riser to the wellhead.

FIG. 3 illustrates, on a larger scale than in FIG. 2, details of thelatching means for coupling the well reentry tool to the wellhead.

FIG. 4 shows a well re-entry tool combined with a drill bit, partly inlongitudinal section.

FIG. 5 shows a longitudinal section through a well reentry tool shapedas a cementing shoe.

FIG. 6 shows a longitudinal section through a well reentry tool of aconstruction different from that shown in FIGS. 1-5.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, a wellhead 1is carried by a base member 2, which incorporates a ball-type joint 3,allowing the base to rest on the sea bottom 4, which may slope withrespect to casings 5 and 6, that are supported by the base member 2 andextend into a well 7. The outer casing 5 has a relatively short lengthand supports a guide means 8, which guide means is used for guiding awell re-entry tool towards well entrance 9.

The guide means 8 consists of a frustoconical member 10 supported by aframe member 11 connected to the upper end of the first casing 5. Themeans 8 also incorporates reflectors 13 carried by the upper rim of thefrustoconical member 10.

The inner casing 6 is suspended in the well 7 from the outer casing 5 bya casing hanger 14.

The well re-entry tool comprises a tube forming the lowermost member ofa string of tubing consisting of a number of tube elements threadablyconnected and suspended from a vessel (not shown in the drawing). Thetube 20 has a jet opening 21 that can be used for jetting a flow ofwater (arrow 22) supplied under pressure at the upper end of the tubingstring. The inner wall of the tube 20 has a seat 23 for supporting anorienting device 24. This device comprises a housing containing theelectronic equipment necessary for operating a rotatable head 26 whichis equipped with means 27 for transmitting acoustic waves as well as fordetecting the reflections of these waves. The housing 25 is within thetube 20, whereas the head 26 is located outside the tube 20 when theorienting device 24 is in the operative position. The housing 25 carriesdriving means (not shown in the drawing) for rotating the head 26 withrespect to the housing 25 and with respect to the tube 20. Theinformation received by the means 27 is passed via a cable 29 to theship (not shown) from which the tube 20 is suspended. The cable 29 isfurther used for carrying the orienting device 24 when it is beinglowered onto the seat 23, or raised therefrom, and for supplying energyto the electronic equipment in the housing 25. Since orienting devicesoperating according to acoustic principles are known per se, no detailsof the modes according to which such devices may operate will bedescribed hereinafter.

A bumper head 30 is connected to the lower end of the tube 20 by meansof a shear pin 31. The lateral dimensions of the bumper head have beenchosen such that when the head is in contact with the inner wall of thefrustoconical guide member 10, the rotatable head 26 is (in allpositions of this head) free from this wall. This is illustrated in FIG.1 by the dashed lines 26' and 30'. Lines 26"- and 30" indicate theposition of the rotatable head and. the bumper head respectively, justprior to the latter entering the entrance 9 of the wellhead 1. Thedashed line 30" indicates the contours of the bumper head in theposition wherein the shear pin 31 has been sheared and the tube 20 (asindicated by the dashed lines 20") has entered the well. The bumper headcan be retrieved from this position by raising the tube which engagesthe bumper head by means of seat 32 on its way upwards.

In operation at a location where the well 7 is known to be positioned,the tube 20 carrying the bumper head 30 at the lower end thereof, andforming part of a tubing string (not shown in the drawing), is loweredto a depth at which the wellhead l is within a range at which thesignals transmitted by the means 27 of the rotating head 26 of theorienting device 24 which has been lowered by cable 29 onto the seat 23of the tube 20 can be received by this means 27.

When the signal contact between the orienting device 24 and thereflectors 13 carried by the conical guide member 10 has beenestablished, the position of the reflectors with respect to the centerof the tube 20 is visible from the display of the signals which aretransmitted to the ship via the cable 29. Subsequently the water jet 22is brought into operation to move the lower end of the tube 20 such thatthe axis thereof will coincide as closely as possible with the center ofthe set of reflectors 13. By rotating the upper end of the tubing stringon board of the ship for varying the direction of the thrust exerted bythe water jet 22, and by varying the pressure of the water supplied tothe tubing string for controlling the magnitude of this thrust, thelower end of the tube 20 can be moved at will.

When the information obtained on board of the ship indicates that theposition of the lower end of the tube 20 is directly above the center ofthe entrance 9 of the well 7, the tube 20 is lowered slowly. Based onthe information obtained from the measuring head 26 of the orientingdevice 24, the position of the lower end of the tube 20 is nowcontrolled by the operation of the jet flow 22 so as to maintain theposition of the lower end of the tube 20 as closely as possible on thecentral axis of the well entrance 9 over the whole range of thisdownward displacement.

The rotating head 26 of the orienting device 24 is protected by thebumper head 30 when the lower end of the tube 20 enters the conicalguide means 10. The bumper head, when in the position 30, will be guidedtowards the well entrance 9 along the inner surface of the guide member10. If desired, the detecting head 26 can be retracted before the bumperhead enters the well entrance 9 (position 30"), but this is notnecessary.

After the bumper head has entered the entrance 9, it is lowered into thecasing 5 until it comes to rest on the casing hanger 14. The weight ofthe tubing string, then shears pin 31 and the tube 20 enters the casing6.

Thereafter a sufficient length of the tubing string, of which tube isthe lowermost element, is lowered into the casing 6 to preventinadvertent retraction of the tube 20 from the casing 6.

Subsequently a marine riser (not shown in the drawing) may be passedover the tube 20, which then acts as a guide for the marine riser toguide the lower end of the riser to the upper end of the casing 5. Tocenter the lower end of the riser with the upper end of the casing 5,centralizers known per se may be arranged on the outer wall of thetubing. The lower end of the marine riser is passed over the top of thecasing 5 and suitable coupling means arranged at the lower end of theriser may be used for coupling the riser to the casing 5 by means oflocking dogs (not shown) cooperating with the annular groove 33 arrangedin the outer wall of the casing 5. The tubing string is then retractedand the tube 20 is retrieved together with the bumper head 30,whereafter the well 7 can be entered by any equipment which is loweredthrough the marine riser from the ship from which the marine riser issuspended.

An alternate embodiment of a well re-entry tool according to the presentinvention is shown in FIG. 2. The guide means used for guiding the lowerend of the tube towards the well entrance differs from the guide meansas shown in FIG. 1, since the well entrance tube 59 in FIG. 2 isprovided with an internal coupling groove for the marine riser.Consequently there is no need for an annular free space between thefrustoconical guide 40 and the well entrance tube 59, and the guide 40is directly in contact with the upper rim of the tube 59. Thefrustoconical guide 40 is supported by columns 41 and 42 which in turnare supported by the frame work 43 connected to and carried by the wellentrance tube 59.

The well re-entry tool according to FIG. 2 can be automatically coupledto the wellhead parts surrounding the well entrance. In this position ofthe well re-entry tool, a tube 51 can be brought under tension byexerting a pulling force thereon from the ship, via the tubing string,so that the string, of which the tube 51 forms the lowermost element,can be applied as a guide for guiding downwards the marine riser 60which is to be coupled to the wellhead. As the lower end of the tubingis coupled to the wellhead, the tube 51 need not be introduced over along distance into the Well to prevent inadvertent retraction therefrom.Thus, the well re-entry tool according to FIG. 2 can be applied forconnecting a guide string to the wellhead which is closed off byblow-out preventers or other suitable means.

The bumper head 50 in FIG. 2 is formed as part of the tube 51 which isthe lowermost element of a tubing string (not shown in the drawing)suspended from a ship (also not shown in the drawing). An orientingdevice 53 is supported by the internal seat 54A of the central opening54 of the bumper head 50, and connected by an electric cable 55 to thevessel. This cable can also be applied for suspending the device 53therefrom. The orienting device 53 has a measuring head 56, whichextends beyond the lower end of the bumper head 50 and can be rotatedwith respect to the bumper head by actuating means (not shown) arrangedwithin the housing of the device 53.

The bumper head 50 further carries a number of latching dogs 57, one ofwhich is shown in FIG. 2 of the drawing. The design of this dog will bedescribed hereinafter in more detail with reference to FIG. 3. The dog57 automatically couples with the groove 58 arranged in the inner wallof the well entrance tube 59 (which forms part of an underwaterwellhead) when the bumper head is sliding downwards in the well entrancetube 59. As can be seen in FIG. 2, the dog 57 locks against movements ofthe bumper head 50 in upward as well as in downward direction, whichmeans that the bumper head cannot be pushed into the well entrance tube59 to such an extent that it will damage the measuring head 56 of theorienting device 53 by coming into contact with the closed blow-outpreventers (not shown) which are arranged to close off the passagethrough the well entrance tube 59. Further, since the bumper head 50 isalso locked against upward movement, the tubing string, of which tube 51forms the lowermost element, can be tensioned from the ship, and can beused as a guide for passing a marine riser string therealong to the wellentrance tube 59 for coupling this riser string at the lower end thereofto the well entrance tube 59.

The marine riser string is suspended from the ship and comprises anumber of tubes, of which tube 60 is the lowermost element. The lowerend of tube 60 is connected to the coupling unit 61 by means of a(schematically indicated) blow-out preventer 64 and a coupling ring 65.The coupling unit 61 comprises locking dogs 66 suitable for cooperationwith an annular groove 67 arranged in the inner wall of the wellentrance tube 59. The locking dogs 66 are operated by an annular piston68 slidably arranged within the cylinder 68A. Since this type ofcoupling is known per se, no further details thereof (such as the hosesand channels for passing hydraulic fluid to and from the cylinderspaces) are shown in the drawing.

The lower rim of the coupling 61 is adapted to actuate a lever 70. Aswill be explained hereinafter, this lever in one position keeps thelocking dog 57 via a spring-loaded rod 71 in the locked position, and ina second position allows the locking dog to be retracted into theopening 72 by spring action when the orienting device 53 has beenretrieved.

The locking dog 57 and the springs used to control the positions of thisdog are shown in FIG. 3 on a scale larger than in FIG. 2.

Referring to FIG. 3, the locking dog 57 forms part of a lever 73, whichis retained in the opening 72 in the wall of the bumper head 50 by meansof an O-shaped spring 74. A ball-shaped knob 75 is connected to thelever 73, which knob is enclosed by a housing 76, in which the knob canoscillate over limited angles. The housing 76 is slidable within asecond housing 77 and a spring 78 is arranged to move the two housingsapart. A stop ring 79 is mounted on the housing 77. The housing 76 ispressed against this ring 79 by the action of the spring 78.

The housing 77 is pressed towards the central axis of the bumper head 50by a spring 80. One end of the spring 80 is supported by a ring member81 screwed into an opening 82 in the body of the bumper head 50, and theother end of the spring 80 acts on an annular part 83 of the housing 77.One end of the housing 77 passes through the opening of the ring 81,whereas the other end 84 of the housing passes through an opening 85 inthe bumper head 50, which opening extends between the opening 82 and thecentral opening 54 of the bumper head 50.

The operation of the locking means shown in FIG. 3 will now be describedwith reference to FIGS. 2 and 3 of the drawing.

By lowering the orienting device 53 onto the seat 54A (FIG. 2), the end84 (FIG. 3) of the housing 77 is pushed outwards with respect to thecentral axis of the bumper head 50 against the action of the spring 80.The top end 86 of the lever 73 is subsequently moved outwards, whereasthe locking dog 57 remains within the opening 72 due to the action ofthe spring 74. The bumper head 50 is lowered onto the wellhead in themanner described hereinbefore with reference to FIG. 1, and protects themeasuring head 56 against damage when entering the guide cone 40 mountedon the well entrance tubing 59. On further lowering, the bumper head 50enters this well entrance tubing 59 with the locking dog 57 in theretracted position. However, the upper end 86 of the lever 73 is forcedinto the opening 72 by the inner wall of the tubing 59 on furtherlowering of the bumper head 50 in this tubing, thereby compressing thespring 78. As a result the locking dog 57 is displaced outwards againstthe inner wall of the tubing 59. Further downward movement of the bumperhead 50 brings the locking dog 57 into line with the annular groove 58(the position as shown in FIG. 2) whereafter the dog 57 snaps into thegroove 58 preventing any further displacement of the bumper head 50 in avertical direction.

Without a stop member 87 in the bumper head 50, the locking dog 57 couldbe uncoupled by pulling the orienting device 53 upwards by the cable 55.This would result in a decrease of the outwardly directed force exertedby the spring 78 on the ball joint 75 of the lever 73, which would inturn result in an inwardly directed displacement of the locking dog 57under influence of the spring 75, thereby retracting the dog 57 from thegroove 58. Thereafter, the bumper head 50 could be retracted from thewell entrance tubing 59.

When guiding the marine riser string 60 (FIG. 2) together with blow-outpreventer 64 and coupling member 61 over the tubing string of which tube51 forms the lowermost member, the cable 55, where it emerges from theupper end of the tubing string, is often a nuisance when the separateelements of the marine riser string have to be passed over the top ofthe tubing string. Therefore, the cable 55 together with the orientingdevice 53 is removed from the tubing string prior to lowering marineriser string 60. Since this action would decouple the latching dog 57, astop member 87 (FIG. 3) is provided which in a first position thereof isbetween the ring 83 on the housing 77 and the end wall of the opening82, and in a second position is retracted so as to allow the ring 83 tocontact the end wall of the opening 82 under the action of the spring80. The stop member 87 is pressed into the first position thereof underinfluence of the rod 71 which is loaded by a spring 71A (FIG. 2). Thusremoval of the orienting device 53 will not influence the position ofthe latching dog 57 as shown in FIG. 2, as the stop member 87 remains inplace. Thus the latching dog 57 remains in the groove 58 to withstandthe upward force exerted on the tube 51.

When the coupling member-61 of the marine riser string 60 has beenguided into the well entrance tubing 59, the lower rim of the member 61will actuate the lever 70, which will retract the rod 71 and the stopmember 87 allowing the latching dog 57 to be pulled out of the groove 58under influence of the spring 74 (FIG. 3). Preferably, the load exertedon the tubing string is removed to facilitate the retraction of thelocking dog 57 from the groove 58.

After the coupling unit 61 has been coupled to the well entrance tubing59 by actuation of the piston 68 displacing the locking dogs 66 intocontact with the groove 67, the tubing string of which the tube 51 isthe lowermost member may be pulled up.

Subsequently the equipment to be used in the well can be lowered throughthe marine riser string into the well.

The application of the well re-entry tool according to the invention isnot limited to the use thereof in combination with a conical guidefunnel. The tool may also be used in combination with a truncatedpyramidshaped guide funnel, which preferably has three or more sideplanes.

A bumper head combined with a drill bit is shown in FIG. 4. The bit isof the roller type comprising a body 100, provided with pins 101 (onlyone of which is shown) around which cutting rollers, such as a cuttingroller 102, are rotatably arranged. The body is provided with a couplingscrew thread 103 to couple the body 100 to a connecting member 104 thatis screwed to the lower end of a tube 105 forming part of a drill string(not shown).

The connecting member 104 comprises a seat 106 for the shoulder 107 ofan orienting device 108 provided at one end thereof with a rotatablemeasuring head 109 and connected at the other end thereof to an electriccable 110.

The measuring head 109 transmits acoustic waves, receives reflections ofthese waves, which are transformed into electric currents and passed tothe ship (not shown) via the electric cable 110.

Openings 111 and 112 are arranged in the connecting member 104 and thebody 100, respectively to allow a flow of mud to pass from the interiorof the tube 105 to the cutting rollers 102.

The drill bit is surrounded by a bumper head 115 which is connected tothe connecting member 104 by break pins 116 at its upper end.

Part of the upper surface of a frustoconical guide member which isadapted to cooperate with the drill bit/bumper head combination shown inFIG. 4 is schematically indicated by the dashed line 1 17. It will beappreciated that, after the combination has been lowered onto thesurface of the guide member the combination is guided to the lower partof the guide member adjoining the well entrance in a manner such thatthe measuring head 109 of the orienting device 108 will not come intocontact with this guide surface and be damaged thereby. Damage of thesurface of the guide member by the teeth of the rollers 102 is preventedby the bumper head 115, the lower rim of which is in contact with theguide surface when the bumper head/bit combination is guided over theguide surface to the well entrance.

After having entered the well on which the guide 117 is mounted, thebumper head 115 may be hampered on its way down by a decrease indiameter of the well entrance. The pins 106 are then sheared off and thebit is lowered into the well by means of the drilling string of whichthe tube 105 forms the lowermost element. Before lowering the bit ontothe bottom of the well, the orienting device 108 is retracted by thecable 1 10, and a drilling insert piece (not shown) is lowered via thedrill string on the seating 106 and locked to the connecting member 104in a manner known per se, so that the cutting elements of this drillinginsert piece together with the cutting rollers 102 form a bit capable ofcutting a full sized hole.

When retracting the bit from the well, the bumper head 115 is picked upagain and retrieved to the ship from which the drilling operations arebeing carried out.

A bumper head which is shaped as a cementing shoe is shown in FIG. ofthe drawing. This bumper head is used for guiding the lower end of acasing into a submerged well entrance by means of acoustic equipment anda frustoconical guide member mounted on the well entrance. The lower endof the casing 120 is provided with a casing shoe 121 having a couplinggroove 122 in the inner wall thereof. A groove 123 in this inner wallcarries a sealing member 124.

The casing shoe 121 carries a cementing shoe consisting of an inner part125 and an outer part 126, both parts being made of drillable material.The outer part 126 of the cementing shoe is supported in the casing shoe121 by means of a locking dog '127 cooperating with the annular groove122. The locking dog is movable around a pin 128 and held in theposition shown in FIG. 5 by the action of a spring 129.

The inner part 125 of the cementing shoe is provided with a latch 130,hingeably mounted on a pin 131 and operated'by a spring 132 to cooperatewith a shoulder 133 of the outer part 126 of the cementing shoe. Theinner part 125 may be pushed in a downward direction into the outer partuntil the shoulders 134 and 134A of these parts cooperate. An annulargroove with sealing member 135 is arranged in the outer part 126 of thecementing shoe to seal the passage between the two parts of thiscementing shoe. The inner part 125 of the cementing shoe further carriesa valve 136 hingeably mounted on a pin 137 and actuated by a spring 138to close the passage 139 through the inner part 125 of the cementingshoe. In the situation shown, the valve 136 is kept in the open positionby the lower end of a cementing tube 140, which is passed through thepassage 139 in the inner part 125 of the cementing shoe and screwed tothis inner part 125 by screw thread 141. When unscrewing the tube 140from the inner part 125 of the cementing shoe, rotation of this innerpart with respect to the casing shoe 121 is prevented by a cam 133A onthe shoulder 133 and by cams (not shown) in the groove 122.

When the lower ends 142 and 143 of the inner and outer cementing shoeparts 125 and 126, respectively, cooperate with the upper surface of aguide cone mounted on a well entrance, they prevent the measuring head144 of an orienting device 145 from becoming damaged by contact with theupper surface of the guide cone. The orienting device 145, when in theposition shown by dashed lines, rests on a shoulder 146 of the cementingtube 140 and is connected to the ship from which the cementingoperations may take place, by an. electric cable (not shown), whichcable can also be used for lowering or lifting the orienting device 145with respect to the cementing tube 140.

The way in which the bumper head/cementing shoe shown in FIG. 5 can beused will now be described.

The outer cementing shoe part 126 is locked to the casing shoe 121 bythe locking dog 127 cooperating with the groove 122 in the part 126 ofthe cementing shoe. Thereafter the casing shoe 121 is screwed to thelower end of the casing which is subsequently lowered into the sea fromthe ship from which the cementing operation is going to take place, byadding casing elements so as to form a casing string of sufficientlength. Subsequently the inner cementing shoe part is screwed to thecementing tube by the screw coupling 141. The part 125 and the tube 140are then introduced into the upper end of the casing string and loweredtherein by adding further cementing tube elements to form a cementingstring. When the inner part 125 is landed on the outer part 126 of thecementing shoe, the inner part is latched to the outer part by the latch130. Further penetration of the inner part 125 into the outer part 126unlatches the dog 127 from the groove 122 by the action of the shoulder147 of the inner part 125.

By further downward movement of the cementing tube 140 with respect tothe casing 120, the two parts 125 and126 of the cementing shoe arepassed out of the casing shoe 121 and lowered so as to expose at a levelbelow the lower end of the casing shoe 121 a jet nozzle (not shown) inthe cementing string 140. In this position the top of the casing string120 is suspended on J-slots on a marine swivel (not shown) placed in thecementing string 140. By adding further cementing tube elements thewhole casing assembly is lowered to a point above the wellhead cone.

The orienting device 145, which has been lowered through the cementingtube string onto the shoulder 146 protrudes with the head 144 thereofthrough the central opening of the cementing shoe. The display of theposition of the measuring head 144 with respect to the (not shown) guidecone mounted on the well entrance, will allow the operator on board theship to take all measures necessary to bring the central axis of themeasuring head into coincidence with the central axis of the guide cone.This can be achieved by displacing the ship or displacing the cementingtube by propulsion means mounted thereon, such as a jet nozzle arrangedin the wall thereof. Since the operation of such a jet nozzle hasalready been extensively explained with reference to FIG. 1, no furtherdescription will be given.

Once the cementing shoe is in close alignment with the well entrance,the cementing tube 140 is lowered onto the guide cone on the wellentrance. Since the measuring head 144 is protected against damage fromthe surface of the guide cone by the presence of the surfaces 142 and143 of the cementing shoe, the head 144 may remain in its operativeposition until the cementing shoe has entered the guide cone, and hasbeen inserted into the well bore far enough to prevent inadvertentwithdrawal of the cementing tube from the wellhead.

Subsequently, the orienting device is retracted}? from the cementingstring and the cementing string 120 is lowered until the top of theasing lands in the wellhead. The marine swivel is tlteri released fromthe J- slots and the cementing string is raised until the cementing shoelatches with dog 127 in the casing shoe 121. Cementing is then effectedthrough the cementing string. After cementing, the cementing string 140is released by unscrewing the coupling 141, and retracted from the well.The central passage 139 through the inner part 125 of the cementing shoeis closed by the valve 136 when the tube 140 is retracted from thispassage, thereby preventing backflow of cement to the interior of thecasing 120. After the cement has set, drilling is resumed in the well byintroducing a bit through the casing string 120. The cementing shoebeing made of drillable material, the drill will pass through the shoeand any cement present therebelow to deepen the well.

Another design of the bumper head according to the invention is shown inFIG. 6. The head 149 forms part of a tube 150 which is arranged at thelower end of a string of tubing (not shown) suspended from a vessel (notshown). The head 149 comprises a plurality of arms 151 which arehingeably mounted around pins 152. The arms are maintained in theposition shown in the drawing by springs 153 which are sufficientlystrong to maintain the arms 151 in their outwardly directed positionwhen the bumper head 149 is lowered onto the upper surface of the guidecone 154 mounted on the frame work 155, which is connected to the casing156 cemented to the sea bottom 157. However, the springs 153 cannotprevent folding of the arms into the recesses 149A when the bumper headis entering the casing 156 since in this position of the bumper head thevertical load thereon is increased by lowering the tubing string ofwhich tube 150 forms the lowermost element.

As shown in FIG. 6, the measuring head 158 of the orienting device 159protrudes through the central opening of the bumper head 158 and isprevented from being damaged by contact with the guide cone 154 by thearms 151 which slide over the upper surface of the guide cone 154 andbridge the annular gap between the cone 154 and the entrance to thecasing 156, thereby keeping the measuring head 158 free from contactwith the guide cone 154 and the casing 156. After the bumper head 149has entered the casing 156, the orienting device 159 is retracted by acable 160.

It will be appreciated that the well re-entry tool according to theinvention can also be used in combination with orienting devices otherthan those described with reference to FIGS. 1-5 of thedrawing. Ifdesired, these orienting devices may operate according to principlesdifferent from the acoustic principle.

An additional advantage of the use of a bumper head according to theinvention is that, when applying such head in combination with a tubecarrying a jet nozzle for displacing the tube laterally with respect tothe wellhead on which it is to be landed, the bumper head masks theacoustic orienting device from direct receipt of high frequency jetnoise. Preferably the top surface of the bumper head slopes at an angleof 45 or more from the longitudinal axis of the tube. The jet noise isthen reflected out at an angle up from the horizontal and away fromobjects on the ocean floor which prevents erroneous signals from beingreceived by the orienting device.

We claim as our invention:

1. A well re-entry tool in combination with a guide funnel mounted on awellhead located adjacent the floor of a body of water, said toolcomprising:

a tube with connecting means at its upper end for mating with anothertube, said tube having an internal seat at its lower end;

an orienting device axially movable within said tube for resting on saidinternal seat, a portion of said orienting device extending below thelower end of said tube; and

a bumper head carried outwardly on the lower end of said tube andextending radially outwardly therefrom to a distance and at an angle toform an outwardly extending lower surface configuration thatprotectively surrounds the portion of said orienting device extendingbelow said bumper head and which contacts the inner wall of the guidefunnel during re-entry operations while maintaining the orienting devicein spaced relation to said inner wall of said guide funnel when thebumper head touches said inner wall in a position in which thelongitudinal axis of the tube and the funnel are substantially parallel.

2. A well re-entry tool of claim 1 wherein the bumper head forms anintegral part of said tube.

3. A well re-entry tool of claim 1 wherein the bumper head is connectedto said tube by at least one shearable 4. A well re-entry tool of claim2 further including latching means carried by the bumper head which canbe moved between two end positions, the latching means being within thewall of the bumper head in a first end position, and extending beyondsaid wall in a second end position thereby locking said bumper headagainst movements parallel to the longitudinal axis of the wellheadcarrying the guide funnel.

5. A well re-entry tool of claim 4 wherein means are provided forretracting the latching means from said second end position to the firstend position.

6. A well re-entry tool of claim 5 wherein the means provided forretracting the latching means are operable by displacement of theorienting device.

7. A well re-entry tool of claim 5 wherein locking means preventing thelatching means from retracting are provided, said locking means beingoperable by a lever extending outside the wall of said bumper head.

8. A well re-entry tool according to claim 1 further including a drillbit connected to the lower end of said tube wherein the bumper head isin the form of a cylindrical shroud encircling the bit and connected atits upper end to the tube by shear pins.

9. A well re-entry tool according to claim 1 wherein the upper surfaceof the bumper head is arranged at an angle of at least 45 with respectto the longitudinal axis of the tube whereby jet noise is reflected outat an angle up from the horizontal and away from objects on the oceanfloor preventing erroneous signals from being received by the orientingdevice.

1. A well re-entry tool in combination with a guide funnel mounted on awellhead located adjacent the floor of a body of water, said toolcomprising: a tube with connecting means at its upper end for matingwith another tube, said tube having an internal seat at its lower end;an orienting device axially movable within said tube for resting on saidinternal seat, a portion of said orienting device extending below thelower end of said tube; and a bumper head carried outwardly on the lowerend of said tube and extending radially outwardly therefrom to adistance and at an angle to form an outwardly extending lower surfaceconfiguration that protectively surrounds the portion of said orientingdevice extending below said bumper head and which contacts the innerwall of the guide funnel during re-entry operations while maintainingthe orienting device in spaced relation to said inner wall of said guidefunnel when the bumper head touches said inner wall in a position inwhich the longitudinal axis of the tube and the funnel are substantiallyparallel.
 2. A well re-entry tool of claim 1 wherein the bumper headforms an integral part of said tube.
 3. A well re-entry tool of claim 1wherein the bumper head is connected to said tube by at least oneshearable pin.
 4. A well re-entry tool of claim 2 further includinglatching means carried by the bumper head which can be moved between twoend positions, the latching means being within the wall of the bumperhead in a first end position, and extending beyond said wall in a secondend position thereby locking said bumper head against movements parallelto the longitudinal axis of the wellhead carrying the guide funnel.
 5. Awell re-entry tool of claim 4 wherein means are provided for retractingthe latching means from said second end position to the first endposition.
 6. A well re-entry tool of claim 5 wherein the means providedfor retracting the latching means are operable by displacement of theorienting device.
 7. A well re-entry tool of claim 5 wherein lockingmeans preventing the latching means from retracting are provided, saidlocking means being operable by a lever extending outside the wall ofsaid bumper head.
 8. A well re-entry tool according to claim 1 furtherincluding a drill bit connected to the lower end of said tube whereinthe bumper head is in the form of a cylindrical shroud encircling thebit and connected at its upper end to the tube by shear pins.
 9. A wellre-entry tool according to claim 1 wherein the upper surface of thebumper head is arranged at an angle of at least 45* with respect to thelongitudinal axis of the tube whereby jet noise is reflected out at anangle up from the horizontal and away from objects on the ocean floorpreventing erroneous signals from being received by the orientingdevice.